Liquid fire and heat retardant compositions can be difficult to use, especially when the liquid is a resinous, viscous material. There are processing and equipment problems in transporting and mixing this type of liquid, on a commercial scale, and in mixing it with fire unstable materials that are light and in particulate form, such as, expandable polystyrene granules, chips or pieces of cellulosic materials and the like.
When a liquid fire retardant is associated with a fire unstable material, the fact that the fire retardant composition is a liquid may be harmful and can prevent its use. There may be an undesired chemical reaction during the production of a fire resistant structure that would deleteriously affect the resulting structure. If the fire retardant composition is intended to be incorporated, for example, in a foam polyurethane structure, its reactivity or presence can prevent or interfere with the isocyanate or polyol ingredients or with the formation of a foamed polyurethane structure. A fire retardant composition in dried powdered form may be used in the production of a fire resistant composition and by virtue of not being reactive will not interfere with production of a useful effective fire resistant structure.
The fact that a powder has a much lower bulk density than a dense, resinous liquid can provide effective protection for a larger amount of fire unstable material, using a less weight of the material, creating economies in the production of fire and heat retardant structures.